QUEZON CITY — Metro Manila and immediate environs maybe facing a new earthquake faultline in addition to the Marikina Valley Fault consisting of the west and east fault segments.
Dr. Kevin Rodolfo, a Filipino geologist, University of Illinois and University of the Philippines professor and consultant for the Department of Science and Technology’s (DOST) project, the Nationwide Operational Assessment of Hazard (NOAH), revealed the discovery of what appeared to be a newly identified fault as he called for further studies on the matter.
There are fears that the West Valley Fault could make a major movement at any time. A risk assessment study funded by the Japan International Cooperation Agency noted that the West Valley Fault had moved four times and generated strong earthquakes within the last 1,400 years.
Rodolfo said he found what initially appeared to be a new fault line while observing land subsidence patterns due to ground water extraction in Metro Manila between 2003 and 2006 using high-tech satellite equipment.
“We used a very high-tech satellite tool called Permanent Scatter Interferometric Synthetic Aperture Radar. In short, the satellite takes images of the earth over time and combines it to show subsidence through various colors,” he said.
The images collected of Metro Manila and neighboring provinces showed yellow to red patches in the towns of Guiguinto, Malolos, Marilao and Obando in Bulacan; Caloocan, Malabon, Navotas, Valenzuela, Manila, parts of Quezon City, Taguig, Pateros, Las Piñas, Muntinlupa; and portions of the provinces of Cavite and Laguna.
But Philippine Institute of Volcanology and Seismology (Philvocs) Director Renato Solidum Jr. said there is no evidence yet that there is a new fault line in Metro Manila, hinting that it may just be part of either the West Fault or East Fault, two segments of the Marikina Fault.
Solidum said there is no indication so far that another active fault line exists and intersects with the West Valley Fault which traverses Marikina City, Pasig City going to Muntinlupa City and San Pedro City in Laguna.
Solidum said Phivolcs has also seen the observations made by Rodolfo, but there could be so many possible interpretations.
“There is one and only active fault in Metro Manila, and that is the West Valley Fault,” he said.
However, Solidum welcomes the possibility raised by Rodolfo and any studies and healthy discussions about new discoveries of faults.
“We need to be extra careful with our evaluation,” he added.
Rodolfo earlier said a vertical displacement and potential fault line cuts across the metro’s center in a straight southwest-northeast direction from Manila Bay.